Hot rolled HARDOX400 wear-resistant steel will produce pits, because bad rolling can also cause surface pits. The surface of hot rolled HARDOX400 wear-resistant steel often appears on the upper and lower surfaces of the HARDOX400 steel plate, and the upper surface is more serious. The shape is polygonal, round or oval, and the distribution is not regular, and no obvious rolling direction is extended. It is a kind of pressure entry form face defect. No slag elements such as Ca and Al were detected at surface pits. The defects were not related to the mold fluxes. The hemp pit was formed by crushing the oxide scale and pressing it onto the surface of HARDOX400 wear-resistant steel. Aiming at this kind of pitting defect consisting only of oxide scale, the improvement measures are as follows:
Optimize the rolling process and control the thickness and structure of the oxide scale. The formation of the pits is related to the final rolling temperature, and the final rolling temperature is easily formed between 810-850 degrees centigrade, and the final rolling temperature of HARDOX400 wear-resistant steel should be increased as much as possible, so that the hardness of the oxide skin on the surface of HARDOX400 wear-resistant steel is kept in a small range, so that the oxide skin in the rolling is not easily pressed into the surface of the middle billet. Laminar cooling can be used to ensure the performance of HARDOX400 steel plate and reduce the thickness of the surface of HARDOX400 steel plate on the cooling bed.
Rationally formulate the descaling process to improve the efficiency of the descaling. When the intermediate billet is rolled into stage II, the effect of first scale descaling should be ensured on the premise that the surface temperature of HARDOX400 wear-resistant steel is allowed. When rolling to the last few times, in order to avoid the formation of a flax defect on the surface of the middle billet of the newly formed three oxide skin, the total descaling should be carried out in the last few ways, and the pressure of the descaling system is guaranteed to be 16-20MPa.
In addition, the fine descaling nozzle should be arranged according to the width of HARDOX400 steel plate, and the time of fine descaling should be adjusted according to the length of HARDOX400 steel plate and the conveying speed of the roller in order to ensure that the high pressure water spray can cover the whole plate.
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